Flight termination system for tethered aerial vehicles

ABSTRACT

Aspects of the disclosure relate to flight termination systems for tethered aerial vehicles. For instance, a flight termination system for a tethered aerial vehicle including an envelope may include a tool and a tether. The tool may include a first piece configured for attachment to an interior surface of the envelope and including a cutting blade. The tool may also include a second piece configured for attachment to an exterior surface of the envelope. The tether may be attached to the first piece such that when in use, a force on the tether causes the tool to cut an opening into the envelope.

BACKGROUND

Tethered aerial vehicles may be employed in various ways, including, forinstance, testing features of high-altitude aerial vehicles, such asballoons, closer to the ground. For example, some systems may providenetwork access via a network including aerial vehicles. To maintain thenetwork, each aerial vehicle may be required to be located at and/or totravel to a particular location, communicate with other aerial vehiclesand ground stations, as well as provide network access. In order toensure that an aerial vehicle will function properly when in use, forinstance for testing purposes as noted above, an aerial vehicle may betethered, or rather, attached to some object on the ground in order tolimit their movement relative to the ground. At some point, when theseserial vehicles need to be brought back to the ground, doing so quicklyand as predictably as possible is critical.

BRIEF SUMMARY

Aspects of the present disclosure are advantageous for high altitudeballoon systems. For instance, one aspect of the disclosure provides aflight termination system for a tethered aerial vehicle including anenvelope. The system includes a tool including a first piece configuredfor attachment to an interior surface of the envelope. The first pieceincludes a cutting blade, and the tool also a second piece configuredfor attachment to an exterior surface of the envelope. The system alsoincludes a tether attached to the first piece such that when in use, aforce on the tether causes the tool to cut an opening into the envelope.

In one example, the second piece includes a handle portion configuredsuch that when the tool is attached to the envelope, the handle portionis angled away from the envelope. In this example, the handle portion isarranged such that when the tool is attached to the envelope, the handleportion overlies the blade. In another example, the second piece furtherincludes a first opening through which the tether is connected. Inanother example, the second piece includes a connection portionincluding at least one opening therethrough. In this example, the firstpiece includes at least one opening therethrough corresponding to the atleast one opening of the connection portion. In addition, the systemalso includes a bolt configured for placement through the at least oneopening of the first piece and the at least one opening of theconnection portion in order to secure the first piece to the secondpiece. In this example, the system also includes envelope materialcorresponding to the envelope, and the bolt is attached to the firstpiece and the second piece via a nut such that the envelope material isarranged therebetween. In addition, the bolt creates a seal between theenvelope material and the first and second pieces. In another example,the system also includes the envelope. In this example, the envelopeincludes a plate and an eye bolt attached to the plate, and wherein thetether is arranged through the eye bolt. In addition, the plate is a topplate arranged at an apex of the envelope. Alternatively, the plate is abase plate arranged at a base of the envelope. In another example, thetether is long enough to enable an operator at ground level to cause theforce by pulling on the tether. In another example, the system alsoincludes as a motorized winch system to which the tether is attached,and wherein the motorized winch system is configured to create theforce. In another example, the tether is configured to be pulledmanually by an operator in order to create the force. In anotherexample, the first piece includes a pair of wing portions that extendlaterally from a body portion of the first piece such that when in use,the wing portions are arranged to assist the tool in sliding along theinterior surface. In another example, the first piece includes a pair ofwing portions that extend laterally from a body portion of the firstpiece such that when in use, the wing portions reduce a likelihood ofthe tool falling out of the envelope.

Another aspect of the disclosure provides a method for terminatingflight of a tethered aerial vehicle having an envelope. The methodincludes causing a force on a tether attached to a flight terminationtool. The tool includes a first piece attached to an interior surface ofthe envelope, a cutting blade, and a second piece attached to anexterior surface of the envelope. The method also includes using theforce on the tether to cause the blade to create an opening in theenvelope in order to terminate flight of the tethered aerial vehicle. Inone example, the tether is arranged through an eye bolt at a plate ofthe envelope, and causing the force includes pulling at least a portionof the tether through the eye bolt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of an aerial vehicle in accordance with aspects ofthe present disclosure.

FIG. 2 is an example of an aerial vehicle in flight in accordance withaspects of the disclosure.

FIG. 3 is an example view of a flight termination system in accordancewith aspects of the disclosure.

FIG. 4 is an example view of a flight termination system in accordancewith aspects of the disclosure.

FIG. 5 is an example view of a flight termination system and portion ofan aerial vehicle in accordance with aspects of the disclosure.

FIGS. 6A and 6B are example views of a first piece in accordance withaspects of the disclosure.

FIG. 7 is an example detail view of a portion of a first piece inaccordance with aspects of the disclosure.

FIGS. 8A and 8B are example views of a second piece in accordance withaspects of the disclosure.

FIGS. 9A and 9B are example flow diagrams in accordance with aspects fthe disclosure.

FIG. 10 is an example flow diagram in accordance with aspects of thedisclosure.

DETAILED DESCRIPTION

Overview

The present disclosure generally relates to providing system forterminating a flight of a tethered balloon having an envelope. Tetheredballoons may be employed in various ways, including, for instance,testing features of high-altitude balloons closer to the ground. At somepoint, when these balloons need to be brought back to the ground, doingso quickly and as predictably as possible is critical. The techniquesand features described herein may allow a user on the ground to activatea flight termination system attached to the balloon that causes theenvelope to release its lift gas in a manner that allows the balloon todescend back to Earth.

The flight termination system may include a cutdown tool and a tether.One end of the tether may be attached to the cutdown tool, for instance,via an opening in the cutdown tool. The tether of the flight terminationsystem may be a different tether from the one that keeps the balloonfrom floating away. In order to enable the tool to create an opening inthe envelope material, the tether may be connected to a top or bottomplate of the envelope in order to provide a consistent direction of apulling force by the tether.

The tool may include first and second pieces. The first piece may beconfigured to be mounted internally to the envelope. The first piece mayinclude a body portion having ends of which are generally orientedtowards one of a respective top plate and bottom plate of the balloon. Afirst end of the body portion may terminate in a curved, rounded orchamfered edge in order to avoid snagging or catching on the envelopematerial. A second end of the body portion includes a slit with a bladearranged within the slit. Adjacent to the blade on the body portion is amounting projection with one or more openings therethrough for placingbolts. The first piece may also include a pair of wing portions whichextend laterally from the body portion. The second piece of the tool mayinclude a handle portion which overlies the blade and a connectionportion including a corresponding one or more openings therethrough forplacing bolts.

The tool may be installed during manufacturing of the envelope or postmanufacturing of a completed envelope. Under normal conditions, the toolwould not cut the envelope material. However, after the balloon isfilled and launched, when a certain amount of force is applied to thetether, the tool may begin cutting the envelope material. The force ofthe tether pulling on the tool may cause the bolts to rip through theenvelope material and the blade to create an opening in the envelopematerial.

The features described herein may enable termination of a flight of atethered balloon in a simple and effective way. Terminating the flightof a tethered balloon can have significant safety implications. However,because the tether pulling on the tool creates an opening in theenvelope quickly, the balloon is more likely to fall to the groundimmediately in a more predictable way which may minimize risk to otherobjects around the balloon.

Example Aerial Vehicle

FIG. 1 is an example aerial vehicle 200 which may be a balloon. Ofcourse, other aerial vehicles may also be tested using tethers. Asshown, the aerial vehicle 200 includes an envelope 210, a payload 220and a plurality of tendons 230, 240 and 250 attached to the envelope210. The envelope 210 may take various forms. In one instance, theenvelope 210 may be constructed from materials (i.e. envelope material)such as polyethylene that do not hold much load while the aerial vehicle200 is floating in the air during flight. Additionally, oralternatively, some or all of envelope 210 may be constructed from ahighly flexible latex material or rubber material such as chloroprene.Other materials or combinations thereof may also be employed. Further,the shape and size of the envelope 210 may vary depending upon theparticular implementation. Additionally, the envelope 210 may be filledwith various gases or mixtures thereof, such as helium, hydrogen or anyother lighter-than-air gas. The envelope 210 is thus arranged to have anassociated upward buoyancy force during deployment of the payload 220.

The payload 220 of aerial vehicle 200 may be affixed to the envelope bya connection 260 such as a cable or other rigid structure. The payload220 may include a computer system (not shown), having one or moreprocessors and on-board data storage. The payload 220 may also includevarious other types of equipment and systems (not shown) to provide anumber of different functions. For example, the payload 220 may includevarious communication systems such as optical and/or RF, a navigationsoftware module, a positioning system, a lighting system, an altitudecontrol system (configured to change an altitude of the aerial vehicle),a plurality of solar panels 270 for generating power, a power supply(such as one or more batteries) to store and supply power to variouscomponents of aerial vehicle 200.

In view of the goal of making the envelope 210 as lightweight aspossible, it may be comprised of a plurality of envelope lobes or goresthat have a thin film, such as polyethylene or polyethyleneterephthalate, which is lightweight, yet has suitable strengthproperties for use as a envelope. In this example, envelope 210 iscomprised of envelope gores 210A-210D.

Pressurized lift gas within the envelope 210 may cause a force or loadto be applied to the aerial vehicle 200. In that regard, the tendons230, 240, 250 provide strength to the aerial vehicle 200 to carry theload created by the pressurized gas within the envelope 210. In someexamples, a cage of tendons (not shown) may be created using multipletendons that are attached vertically and horizontally. Each tendon maybe formed as a fiber load tape that is adhered to a respective envelopegore. Alternately, a tubular sleeve may be adhered to the respectiveenvelopes with the tendon positioned within the tubular sleeve.

Top ends of the tendons 230, 240 and 250 may be coupled together usingan apparatus, such as top plate 201 positioned at the apex of envelope210. A corresponding apparatus, e.g., bottom plate 214, may be disposedat a base or bottom of the envelope 210. The top plate 201 at the apexmay be the same size and shape as and bottom plate 214 at the bottom.Both caps include corresponding components for attaching the tendons230, 240 and 250 to the envelope 210.

FIG. 2 is an example of aerial vehicle 200 in flight when the envelope210 is pressurized. In this example, the shapes and sizes of theenvelope 210, connection 260, and payload 220 are exaggerated forclarity and ease of understanding. During flight, these aerial vehiclesmay use changes in altitude to achieve navigational direction changes.For example, the altitude control system of the payload 220 may causeair to be pumped into a ballast within the envelope 210 which increasesthe mass of the aerial vehicle and causes the aerial vehicle to descend.Similarly, the altitude control system may cause air to be released fromthe ballast (and expelled from the aerial vehicle) in order to reducethe mass of the aerial vehicle and cause the aerial vehicle to ascend.

In both FIGS. 1 and 2 , a tether 280 is attached to the aerial vehicle200. The tether 280 may be attached to an anchor 290 or other object atground level or on a ground surface of the Earth. This tether may belong enough to enable the aerial vehicle to ascend to altitudes wherethe aerial vehicle is able to pressurize while keeping the aerialvehicle from floating away.

Example Flight Termination System

As noted above, in order to enable an operator to termination flight ofa tethered aerial vehicle, a flight termination system may be used.FIGS. 3 and 4 are views of a flight termination system 300. The flighttermination system 300 may include a cutdown tool 310 and a tether 320.One end 322 of the tether 320 may be attached to the tool 310, forinstance, via an opening 332 in the cutdown tool. The tether 320 of theflight termination system may be a different tether from the tether 280that keeps the aerial vehicle from floating away. The tether 320 may bea rope, cord, or other length of material that does not put too muchweight on the balloon during normal use (i.e. does not prevent theballoon from rising away from the ground surface).

As shown in FIG. 5 , the flight termination system 300 may be mounted tothe envelope 210 between two plates 501, 502. For ease of understanding,the size of the flight termination system 300 relative to the envelope210 is greatly exaggerated, the length of the tether between the plate501 and ground surface is also significantly reduced, and the locationof the ground surface relative to the envelope is arbitrary. Inaddition, aspects of the tool 310, including bolt 380, first piece 330,second piece 340, and nut 384 are depicted as “broken out” in order todepict the relative locations of the various aspects.

In order to enable the tool 310 to create an opening in the envelope210, the tether 320 may be connected to a top plate 201 or bottom plate214 of the envelope 210 in order to provide a consistent direction of apulling force by the tether 320. In one instance, the tether 320 may bearranged through an eye bolt 520 arranged on plate 501. Alternatively,rather than an eye bolt, the tether 320 may be connected to a motorizedspring retraction device or solenoid with a receiver configured toactivate a pulling force and/or wind the tether and cause the tool tocreate the opening.

If the tether 320 is attached at the top plate 201 (i.e. plate 501represents the top plate 201), the tool 310 may be arranged to cut anopening in a downward direction (i.e. arrow 510 would point towards theground surface). If the tether 320 is attached at the bottom plate 214(i.e. plate 501 represents the bottom plate 214), the tool 310 may bearranged to cut an opening in an upward direction (i.e. arrow 510 wouldpoint away from the ground surface).

In one example, the tether 320 may be long enough to extend to theground surface so as to enable an operator or other machine such as amotorized winch system to pull on the tether to create an opening in theenvelope. In this regard, as show in FIG. 5 , a second end 324 of thetether 320 is attached to a motorized winch system 420 which may belocated at the ground surface.

Returning to FIG. 3 , the tool may include first and second pieces 330,340. FIGS. 6A and 6B are example views of the first piece 330. The firstpiece 330 may be configured to be mounted internally to the envelope 210as shown in FIG. 5 . The first piece 330 may include a body portion 350having ends 352, 354 of which are generally oriented towards one of arespective top plate 201 and bottom plate 214 of the aerial vehicle 200.A first end 352 of the body portion may terminate in a curved, roundedor chamfered edge in order to avoid snagging or catching on the envelopematerial. Between the first end 352 and the second end 354 of the bodyportion 350 includes a slit 356 with a blade 360 arranged within theslit. Turning to FIG. 7 which provides a detail view of the first piece330, the blade 360 may be secured in the slit by a threaded bolt 362,screw or other device arranged in an opening in a side surface 358 ofthe body portion 350. The shape of the blade 360 may be selected basedupon the envelope material. For example, some materials may slice with asharp blade more easily than others. Adjacent to the blade 360 on thebody portion 350 is a mounting projection 370 with one or more openings372, 374 therethrough for placing bolts 380, 382. The first piece 330may also include a pair of wing portions 390, 392 which extend laterallyfrom the body portion 350.

FIGS. 8A and 8B are perspective views of the second piece 340. Thesecond piece 340 of the tool 310 may include a handle portion 342 whichoverlies the blade 360 (shown in FIGS. 3 and 4 ) and a connectionportion 344 including a corresponding one or more openings 346, 348therethrough for placing the bolts 380, 382.

As depicted in the example flow diagrams of FIGS. 9A and 9B, the tool310 may be installed during manufacturing of an envelope or postmanufacturing of a completed envelope. For instance, turning to FIG. 9A,prior to completion of the envelope 210, as shown in block 910, thefirst piece 330 may be arranged on one side of the envelope materialwhich will become an interior surface 512 of the completed envelope 210,and as shown in block 920 the second piece 340 may be arranged onanother side of the envelope material which will become an exteriorsurface 514 of the completed envelope. At block 930, one or more bolts380, 382 may be placed into the one or more openings 372, 374 of thebody portion 350 and the one or more openings 346, 348 of the secondpiece. As shown in FIG. 5 , the bolts may be placed through the one ormore openings from the interior of the envelope 210, such that they passthrough the envelope 210 from the interior surface towards the exteriorsurface. The bolts 380, 382 may simply punch through the envelopematerial or one or more prearranged cuts may be made in the envelopematerial in order to allow the bolts to more easily pass through theenvelope material. Thereafter, one or more washers may be placed on theone or more bolts, and, as shown in block 940, one or more nuts 384, 386(see, e.g. nut 384 of FIG. 5 ) may be secured to the one or more bolts(external to the envelope 210 as shown in FIG. 5 ). At this point, theenvelope material may be sandwiched between the first and second pieces330, 340, and the bolts 380, 382 may provide an airtight or nearlyairtight seal with the envelope material.

Alternatively, turning to FIG. 9B at block 950, an opening may becreated, such as by punching or slicing into the envelope material of acompleted envelope, for example, where the envelope 210 and gores arecompleted and have already been attached to the top and bottom plates201, 214. At block 960, the first piece 330 may be placed through theopening, and positioned against the interior surface 512 of the envelope210. At block 970, the second piece 340 may be placed on the exteriorsurface 5145 of the envelope 210, and as shown in block 980 and 990, thebolts 380, 382, washers, and nuts 384, 386 may be installed as describedabove. Thereafter, the opening created in the envelope material of thecompleted envelope may be closed, for instance by heat sealing a patchof additional envelope material over the opening.

Under normal conditions, the tool 310 would not cut the envelopematerial. However, after the envelope of the aerial vehicle is filledand the aerial vehicle is launched, when a certain amount of force isapplied to the tether 320, for instance by pulling on the tether 320manually or using the motorized winch system, the tool 310 may begincutting the envelope material of the envelope 210. The force of thetether 320 pulling on the tool 310 may cause the bolts 380, 382 to ripthrough the envelope material and the blade 360 to create an opening inthe envelope material. Eventually, the one or more bolts 380, 382 wouldbe released from the envelope material when the one or more openings346, 348, 372, 374 of the first and second pieces meet the openingcreated by the blade 360. The cutting action may continue for as long asforce is applied.

For example, FIG. 10 is an example flow diagram for terminating flightof a tethered aerial vehicle having an envelope, such as aerial vehicle200 having envelope 210. In this example, at block 1010, a force iscaused on a tether, such as tether 320, attached to a flight terminationtool, such as tool 310. In this example, the tool including a firstpiece, such as the first piece 330, attached to an interior surface ofthe envelope and having a cutting blade and a second piece, such assecond piece 340, attached to an exterior surface of the envelope. Thismay be achieved, for instance, by an operator pulling on the tether 320manually or, for instance, by using the motorized winch system 420. Atblock 1020, the method also includes using the force on the tether tocause the blade to create an opening in the envelope in order toterminate flight of the tethered aerial vehicle.

When in use, the handle portion 342 of the second piece 340 may beangled away from the envelope 310 which may reduce or preventinterference of the tether 320 and handle portion 342 with the envelopematerial during use. In addition, the shape of the handle portion 342may increase cutting forces as the handle portion may provide someleverage to the point of engagement with the envelope material.

When in use, the wing portions 390, 392 of the first piece 330 mayassist the first end 352 of the body portion 350 to slide along theinterior surface of the envelope 210 and reduce a likelihood of the tool310 “falling out” or off of the envelope 210 while cutting. In someinstances, the tool 310 may remain engaged with the envelope materialeven when at the end of its travel along the envelope 210. The wingportions 390, 392 may also prevent envelope material from bunching upagainst the blade 360 as the tool 310 cuts open the envelope material.As such, the wing portions 390, 392 may provide greater stability duringuse of the tool.

The features described herein may enable termination of a flight of atethered aerial vehicle in a simple and effective way. Terminating theflight of a tethered aerial vehicle can have significant safetyimplications. However, because the tether pulling on the tool creates anopening in the envelope quickly, the aerial vehicle is more likely tofall to the ground immediately in a more predictable way which mayminimize risk to other objects around the balloon.

Most of the foregoing alternative examples are not mutually exclusive,but may be implemented in various combinations to achieve uniqueadvantages. As these and other variations and combinations of thefeatures discussed above can be utilized without departing from thesubject matter defined by the claims, the foregoing description of theembodiments should be taken by way of illustration rather than by way oflimitation of the subject matter defined by the claims. As an example,the preceding operations do not have to be performed in the preciseorder described above. Rather, various steps can be handled in adifferent order or simultaneously. Steps can also be omitted unlessotherwise stated. In addition, the provision of the examples describedherein, as well as clauses phrased as “such as,” “including” and thelike, should not be interpreted as limiting the subject matter of theclaims to the specific examples; rather, the examples are intended toillustrate only one of many possible embodiments. Further, the samereference numbers in different drawings can identify the same or similarelements.

1. A flight termination system for a tethered aerial vehicle includingan envelope, the system comprising: a tool including a first piececonfigured for attachment to an interior surface of the envelope, thefirst piece further including a cutting blade, and the tool furtherincluding a second piece configured for attachment to an exteriorsurface of the envelope; and a tether attached to the first piece suchthat when in use, a force on the tether causes the tool to cut anopening into the envelope.